Method of determining the tensile strength of iron and steel



Nov, 3, 1931. B. D. ENLUND 1,829,793

METHOD OF DETERMINING THE TENSILE STRENGTH OF IRON AND STEEL Original Filed Aug. 16, 1927 SPEc. ELEC. RESLSTANCE INVENTOR.

8202 D4 wo [m U/VD.

Patented Nov. 3, 1931 UNITED STATES,

PATENT OFFICE,

BROB DAVID ENLUND, OF DEGERFORS, SWEDEN, ASSIGNOR TO HENNING ENL'UND, OB

' BINGHAMTON, NEW YORK METHOD OF DETERMINING THE TENSILE STRENGTH OI IRON AND STEEL Original application filed August 16, 1927, Serial No. 213,298. Divided and this application filed March 5,

Y 1929. Serial No. 344,860.

The primar object of my invention is to provide a met 0d of determining the tensile stren h of iron and steel, by the use of speci 0 electric resistance measurements of test pieces thereof, and comparing such measurements with known factors.

-Another object of my invention is to provide a method of this character whereby the result can be directly determined from a chart without the necessity of making calcu lations.

A further object of my invention is to provide such a method which is readily adaptable for use both at the furnaces or point of manufacture as well as in the laboratories and places of use. By my invention, the tensile strength of iron and steel may be determined readily and quickly without the necessity of 'ma'thematical calculations, thus making it possible to rapidly test the material for this characteristic, and to do so with relatively unskilled labor.

It should be stated at the outset that if in the manufacture of iron or steel varying heat treatments are used, the specific electric resistance of the material will necessarily vary with said treatments. It is also well known that variations in the amount of a foreign substance in iron or steel, such as carbon, results in a variation of the tensile strength thereof. '1 have found that there is a direct relation between the specific electric resistance of iron and steel and the tensile strength thereof governed "the foreign substances therein and the treatment of the iron and" steel in the making. Therefore, if the grade of iron and steel, as to foreign substance and treatments, be expressed by an empirical factor, there is obviously a direct relation between this factor and the specific electric resistance'of the material, from which can be determined the tensile strength thereof.

Suitable charts have been prepared by means of which readings may be made by direct comparison between the known factor of a given material and the specific electric resistance measurement. These charts have been prepared with a view to eliminate all necessity of calculations in order that accurate readings may be made by an unskilled party or one not familiar with the mathematical calculations necessary to determine the tensile strength of a given material. This application is a division of my former application Serial No. 213,296 filed August 16, 1927 now Patent No. 1,718,687.

Reference should now be had to the figures of the accompanying drawings forming a part of this application and'wherein like reference numerals indicate like parts.

In the drawings Figure 1 is a diagrammatic view illustrating a form of apparatus for measurin the specific electric resistance of the material to be tested.

Figure 2 is a plan view of a chart used in connection with the resistance measuring apparatus and upon which the tensile strelngth of the material to be tested can be rea It should be here stated that the particular apparatus which is shown in the drawings is illustrative only of a type applicable for measuring the specific electric resistance of the material to be tested. This apparatus forms no part of my invention herein .described and claimed, and many forms of apparatus may be substituted for that shown. In fact, any suitable specific electric resistance measuring apparatus may be employed in carrying out my invention. Likewise, the specific type of chartillustrated is representative only as other forms of charts or scales could be substituted therefor without departing from the spirit and scope of my invention.

In carrying out my invention and method for determining the tensile strength of for instance steel, a length of steel of a given grade and having for instance a known factor of 2.5, representing the foreign substance 2 also comprise contact members and are included in the circuit with the voltmeter 4.

' The contact members 3 lie in a circuit which includes a source of current such as a battery 5, a switch 6, an ammeter 7 and one or more rheostats 8. With the test bar now supported in the clamps 2, and the contacts 3 engaging the ends thereof, the switch is closed allowing the current from the battery 5 to pass through the test bar and. register upon the voltmeter and ammeter, readings from which the specific electric -resistance of the test bar in micro-ohms can be readily computed. As before stated, if desired, an apparatus containing instruments upon which may be read directly the specific electric resistance in micro-ohms may be used.

' tral scale is indicated at 10. On the opposite side or to the right of the scale 10 is a scale 11 calibrated in this instance in kilos per square millimeter representing the units of tensile strength to be measured. If. therefore. after measuring'the specific. electric resistance of the test bar of the grade of steel for which this chart is prepared. in the above described manner. the specific electric resistance isnoted on scale 10 and a straight edge 12 is laid across such scale between that point and the factor point 2.5 to the left of the scale, the tensile strength of the steel may be read at the opposite end of the straight edge on the scale 11. Therefore, by comparison between the specific electric resistance of a known grade and character of steeL'with a common factor expressing such grade and character, the tensile strength thereof is determined.

Obviously. many changes may bemade by way of detail in the form and method of use of my invention without departing from the spirit and scope thereof. I do not limit myself. therefore, to the forms shown and described herein other than by the appended claims.

I claim 1. The method of determining the tensile strength of iron and-steel comprising the steps of measuring the specific electric resistance of a piece of material to be tested and comparing such measurement with a known ment of I- 'said' material.

2. The method of determining the tensile factor representative of the grade and treatstrength-of iron and steel, comprising the steps of measurin the specific electric resistance of a piece 0 the material to be tested, and multiplying such measurement by a known factor determined by the treatment of said material, on a chart upon which can be directly read the tensile strength.

In testimon whereof, I aflix my signature.

ROR DAVID ENLUND. 

